坎地沙坦不同治疗时机对2型糖尿病KK／Ta小鼠肾脏晚期糖基化终末产物形成及其受体表达的影响

Candesartan early or late treatment reduced advanced glycation end-products accumulation and thereceptor for AGE （RAGE） expression in type 2 diabetic KK/Ta mice kidney

目的探讨血管紧张素Ⅱ受体拮抗剂坎地沙坦治疗对自发性2型糖尿病KK／Ta小鼠肾脏晚期糖基化终末产物形成及其受体（RAGE）表达的影响。方法KK／Ta小鼠（n=72）随机分为非治疗组（n=24）；早期治疗组（n=24）：自6周龄起经口予坎地沙坦[4mS／（kg·d）]治疗；晚期治疗组（n=24）：自12周龄起予坎地沙坦治疗。正常对照组采用BALB／c小鼠（n=24）。应用免疫荧光和免疫组化染色检测肾脏中晚期糖基化终末产物一羧甲基赖氨酸（CML）、RAGE蛋白的表达，竞争性RT-PCR检测RAGEmRNA的表达，同时测定尿白蛋白排泄率，血压和糖耐量等临床指标。结果28周龄KK／Ta小鼠尿白蛋白／尿肌酐比率显著增加[（427．494±89．37）mg／gvs（9．544±3．25）mg／g，P〈0．01]，足细胞RAGEmRNA和蛋白表达上调，CML的形成增加。坎地沙坦治疗显著减少了KK／Ta小鼠尿白蛋白／尿肌酐比率[早期治疗组（32．184±9．41）mg／g，晚期治疗组（53．204±26）mg／g，P〈0．01]，抑制肾脏RAGE mRNA和蛋白的表达，减少CML的形成，但早期治疗组和晚期治疗组的作用比较差异无统计学意义（P〉0．05）。结论坎地沙坦治疗通过下调糖尿病状态下肾脏RAGE的表达，阻断AGEs-RAGE的相互作用，减少AGEs的生成，发挥其降低尿白蛋白排泄率和改善肾脏病理损害的保护作用。

Objective The effects of candesartan, an angiotensin II type 1 receptor blocker （ARB） were investigated on advanced glycation end-products accumulation and the receptor for AGE （RAGE） expression in type 2 diabetic KK/Ta mouse kidneys. Methods KK/Ta mice （ n = 72）were ran- dom divided into three groups （ n = 24） and it was treated with candesartan [ 4 rag/（ kg · d） ] or vehiclefrom 6 or 12 to 28 weeks of age. BALB/c mice（ n =24） treated with vehicle were used as controls. Body weight, blood pressure, blood glucose, urinary microalbumin, urinary creatinine and serum creatinine were measured every four weeks. At 28 weeks, renal expressions of carboxymethyllysine and RAGE were evalua- ted by immunohistochemistry and/or competitive RT-PCR. Results KK/Ta mice developed high body weight, high blood glucose, and high urinary microalbumin/creatinine ratio in KK/Ta mice at 28 weeks of age, and it was significantly higher than that of BALB/c mice [ （427. 49 ± 89. 37）mg/g vs （9. 54± 3.25 ） mg/g, P 〈0.01 ]. Protein and mRNA expressions of RAGE were upregulated in KK/Ta kidneys with in-creased immunostaining intensities of carboxymethyllysine. Candesartan treatment has markedly reduced uri- nary microalbumin/creatinine ratio [ Early treatment groulp （ 32. 18 ± 9.41 ） rag/g, Late treatment group （53. 20±7. 26）rag/g, P 〈0. 01 ]. Treatment with candesartan down-regulated the protein and mRNA ex- pressions of RAGE and reduced the accumulation of carboxymethyllysine. There were no significant differ- ences between the two treatment groups （from 6 or 12 weeks）. Conclusions The results suggest that can- desartan, an ARB, reduces advanced glycation end-products accumulation and subsequent allbuminuria by down-regulating RAGE expression in type 2 diabetic KK/Ta mouse kidneys.